Groundwater flow modeling is generally used to define the quantity of groundwater available or direction of dissolved contaminant migration. It is also used to define the limits of a capture zone for a contamination recovery well (or well field), or for delineating a water well protection area (or recharge area) for a water supply. Groundwater scientists frequently use analytical means to model these situations using the classical mathematical formulas to estimate the effect on the groundwater surface. In order to estimate the long-term yield and water-level drawdown of a recovery or water supply well (or well field) they often use the classical formulas for making projections.
Modeling by manual calculations (analytical modeling) can be very time-consuming and, therefore expensive. Therefore,groundwater scientists have prepared a number of computer groundwater modeling programs that allow for a more rapid and efficient assessment of groundwater flow under conditions that may involve the addition of simulated wells and/or simulated sources of recharge in an existing flow field. The models often generate contour maps that illustrate relevant data that are related to groundwater flow. The computer output is usually plotted as groundwater elevation (or artesian pressure) maps for further analysis.
Groundwater scientists have used a number of
different computer models to evaluate the transport of various dissolved organic and
inorganic compounds in groundwater in a number of geologic situations. One
frequently encountered modeling situation involves the assessment of the distribution of
hydrocarbon concentrations around a contaminant source to evaluate various remedial
scenarios including removal of the source of contamination, concentration reductions
resulting from consumption by microbes, effect of groundwater recovery wells, and recharge
sources. The illustration on the right shows a simple grid layout for solute
transport modeling. Such models can be used to predict the time required for
aquifer cleanup or for natural concentration reductions by existing processes in the
subsurface.
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